Chapter 12 - Nervous Tissue Flashcards Preview

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Flashcards in Chapter 12 - Nervous Tissue Deck (45)
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1

Nervous system is responsible for all our __, ___ and __. 

behaviors

memories 

movements

2

neurology

branch of medical science that deals with normal functioning & disorders of the NS

3

Major structures of the NS 

12 pairs of cranial nerves

31 pairs of spinal nerves 

ganglia outside CNS - small masses of nervous tissue, mostly neuronal cell bodies

Enteric plexuses - help regulate digestive system - neuron networks in walls of GI tract organs 

sensory receptors - structure of NS that monitors change in internal/external environment 

4

Functions of NS (3) 

1) sensory - afferent 

2) integrative - interneurons

3) motor - efferent

5

NS divisions (2) 

CNS  - brain & spinal cord

PNS - cranial & spinal nerves, connects CNS to muscles/glands/sensory receptors

6

Neurons

functional unit of nervous system

have capacity to produce action potentials - electrical excitability 

cell body (soma) - contains organelles

Nissl bodies - clusters of rough ER

neurofibrils - cell shape & support

microtubules - assist in moving materials 

dendrites & axons - processes

lipofuscin - yellow/brown pigment granules in cytoplasm

7

Location for most protein synthesis in Neuron

cell body

8

Axonal transport 

1) slow axonal flow

2) fast axonal flow

1) movement in one direction  -away from cell body

2) either direction - use or recycling 

9

Structural classification of neurons

1) multipolar

2) bipolar

3) unipolar

10

Functional classification of Neurons

1) sensory (afferent) 

2) motor (efferent) 

3) interneurons (association) 

11

Neuroglia 

non-neuronal cells

1/2 the volume of CNS 

Of CNS: astrocytes, oligodendrocytes, microglia, ependymal

Of PNS: Schwann, satellite

12

Neuroglia of CNS 

1) astrocytes

2) oligodendrocytes

3) microglia

4) ependymal 

1) support, blood-brain barrier, homeostasis, 

2) form myelin sheath around axons

3) phagocytes

4) produce cerebrospinal fluid 

13

Neuroglia of PNS

1) schwann cells

2) satellite 

1) form myelin sheath around ONE axon 

2) structural support & regulate exchange of materials b/w soma & interstitial fluid

14

Schwann cell cytoplasm forms outer layer & inner layer is...

myelin sheath (100+ layers of schwann cell membrane) 

15

Subdivisions of PNS 

1) Somatic (voluntary) - cutaneous &special sensory receptors → CNS 

motor neurons → skeletal muscle

2) Autonomic (involuntary) - sensory- visceral organs → CNS

motor to smooth+cardiac muscle& glands

A. Sympathetic - ↑ heart rate

B. Parasympathetic - ↓ heart rate

3) Enteric - involuntary sensory & motor control GI tract 

function independently of ANS & CNS 

16

Neurons are electrically excitable due to  the?

voltage difference across their membrane

17

Neurons communicate with (2) types of electric signals

1) action potentials - long distance 

2) graded potentials - short distance

18

Resting membrane potential

What is potential energy difference at rest?

When neuron is at rest,

negative ions along inside of cell membrane & positive ions along outside 

 

-70mV

 

19

At rest, Neuron is said to be _____

polarized

20

Resting potential exists because? (3) 

1) ion concentration differs from inside to outside

ECF has lots of Na+ & Cl-

cytosol has lots of K+

2) inability of most anions to leave cell - membrane permeability differs for Na+ & K+

3) Electrogenic nature of Na+/K+  ATPase

- inward flow of Na+ cant keep up with outward flow of K+ ( Na+ pumped out as fast as it leaks in) 

this removes more positive than it brings in 

21

Graded potential

occur mainly in?

dendrites & neuronal cell bodies 

small deviation from resting potential of -70mV

22

hyperpolarizing vs depolarizing 

hyperpolarizing - membrane becomes more negative

depolarizing - membrane become more positive

23

Graded potential

The signals are graded, meaning they vary in... and are? (2) 

 

1) amplitude (size), 
depending on the strength of the stimulus 

2) localized 

24

Action Potential (impulse) 

a sequence of rapidly occurring events that decrease and eventually reverse the membrane potential (depolarization) and then restore it to resting state (repolarization

25

All-or-none principle of Action Potentials

if stimulus reaches threshold, the action potential produced is always the same

stronger stimulus does NOT produce large impulse

26

(3) phases of an action potential

1) depolarizing phase

2) repolarizing phase

3) hyperpolarizing phase

27

1) depolarizing phase

 

At rest: inactivation Na+ gate = open, activation gate = closed

chemical/mechanical stimulus → graded potential reaches threshold (-55mV) → Na+ channels open → inactivation gate closes  → membrane potential = +30mV 

 

 

 

 

28

 

 

2) repolarizing phase

 

 

when threshold potential reached (-55mV) → K+ channels open (much slower than Na+ channels) → once K+ channels are open, Na+ channels are closed again → K+ outflow returns membrane potential to -70mV

 

 

 

29


3) hyperpolarizing phase
 

if enough K+ leaves cell, membrane potential reaches -90mV 

K+ channels close & membrane potential returns to resting potential (-70mV) 

30

Refractory period

 

Period of time during which neuron can not generate another action potential